Suggest removing value from break when invalid

Author: estebank

src/librustc_passes/loops.rs

@@ -119,6 +119,11 @@ impl<'a, 'hir> Visitor<'hir> for CheckLoopVisitor<'a, 'hir> {
                                              kind.name())
                                 .span_label(e.span,
                                             "can only break with a value inside `loop`")
+                                .span_suggestion(e.span,
+                                                 &format!("instead, use `break` on its own \
+                                                           without a value inside this `{}` loop",
+                                                          kind.name()),
+                                                 "break".to_string())
                                 .emit();
                         }
                     }

src/test/ui/loop-break-value-no-repeat.stderr

@@ -3,6 +3,10 @@ error[E0571]: `break` with value from a `for` loop
    |
 22 |         break 22 //~ ERROR `break` with value from a `for` loop
    |         ^^^^^^^^ can only break with a value inside `loop`
+help: instead, use `break` on its own without a value inside this `for` loop
+   |
+22 |         break //~ ERROR `break` with value from a `for` loop
+   |         ^^^^^
 
 error: aborting due to previous error